1. Field of the invention
This invention relates generally to transient elimination or suppression systems and more particularly, it relates to an improved apparatus and method for attenuating high frequency transients in the range of 50 KHz to 200 MHz on AC power lines from damaging sensitive electrical and electronic circuits in equipment coupled to the AC power lines.
2. Description of the Prior Art
As is generally well-known in the art, modern electrical and electronic circuits in equipment, such as those that exist in microprocessors and computer systems, can be damaged or destroyed by voltage surges, transients, atmospheric discharges (i.e., lightning strikes), and other forms of undesirable electrical noise generated by motors, generators and the like which can cause interferences. As a consequence, there have been developed heretofore many types of transient suppression apparatuses for eliminating unwanted transient voltages or currents and for isolating such transients appearing on the AC external power lines so as to protect sensitive electrical and electronic circuits and equipment coupled to the external power lines.
A prior art search directed to the subject matter of this application in the U.S. Patent and Trademark Office revealed the following U.S. Letters Patent:
In U.S. Pat. No. 5,532,897 to Carpenter, Jr. issued on Jul. 2, 1996, there is taught a high voltage substation level surge suppression system which includes a high energy surge arrestor and a low energy surge arrestor. A surge interceptor is interconnected between the two surge arrestors. The surge interceptor includes an inductor interconnected in parallel with a high energy resistor.
In U.S. Pat. No. 5,671,110 to McCartney et al. issued on Sep. 23, 1997, there is disclosed an apparatus for protecting a non-isolated data communication cable against ground skew used with an AC power source. A current summing transformer is coupled to the AC power source. The current summing transformer includes a single transformer core and a plurality of coils. One of the coils is connected with each phase, neutral and ground line in the AC power source. The current summing transformer provides a high impedance to surge current in the data cable ground of one or many non-isolated data cables.
In U.S. Pat. No. 5,737,161 to Thomas issued on Apr. 7, 1998, there is disclosed an overcurrent protection device which includes a relay having two coils wound on a common magnetic core and a PTC device coupled in parallel with the relay contacts. The first coil is a low impedance current coil, and the second coil is a high impedance voltage coil.
The remaining patents listed above but not specifically discussed are deemed to be of general interest and to show the state of the art pertaining to transient surge suppressors utilizing coils and cores.
Further, there is known in the prior art of U.S. Pat. No. 5,689,130 to Carlson issued on Nov. 18, 1997. This ""180 patent teaches an isolated electrical power supply for protecting electrical devices from transient voltages and currents. A filter is provided which includes a toroid and a resistor which are used in conjunction with an isolator transformer. The filter is coupled between the secondary neutral lead of the transformer and the secondary ground lead so as to shunt the current or voltage spikes. A ferrite bead is connected between earth ground and a binding post for filtering current in the 70-200 KHz range.
However, none of the prior art discussed above teach an apparatus for attenuating high frequency transients on AC power lines like that of the present invention which includes a continuous attenuator circuit for attenuating high frequency transients in the frequency range of 50 KHz to 200 MHz electrically coupled between earth ground and an electrical load ground. The present invention represents significant improvement over the prior art discussed above.
Accordingly, it is a general object of the present invention to provide an improved apparatus for attenuating high frequency transients over a wider frequency range than has been traditionally available.
It is an object of the present invention to provide an improved method and apparatus for attenuating high frequency transients in the range of 50 KHz to 200 MHz on AC power lines from damaging sensitive electrical and electronic circuits and equipment coupled to the AC power lines.
It is another object of the present invention to provide an improved method and apparatus for attenuating high frequency transients which includes a continuous attenuator circuit formed of a plurality of toroid cores.
It is still another object of the present invention to provide any improved method and apparatus for attenuating high frequency transients which includes an isolation transformer and a continuous attenuator circuit.
It is yet still another object of the present invention to provide an improved apparatus and method for attenuating high frequency transients which includes a Ground Fault Circuit Interruptor and a continuous attenuator circuit.
In accordance with a preferred embodiment of the present invention there is provided an apparatus for attenuating high frequency transients on AC power lines from damaging sensitive electrical and electronic circuits in an electrical load coupled to the AC power line. The AC power line has an earth ground and the electrical load has an electrical load ground. An isolation transformer is provided which has a primary winding and a secondary winding. The primary winding has a primary source lead, a primary neutral lead, and a primary electrostatic shield lead. The secondary winding has a secondary source lead, a secondary neutral lead, and a secondary electrostatic shield lead. The primary source lead, primary neutral lead, and primary electrostatic shield lead are electrically coupled to the AC power lines.
The secondary source lead, secondary neutral lead, and secondary electrostatic shield lead are electrically coupled to the electrical load. The primary electrostatic shield lead and the secondary electrostatic shield lead are electrically connected together and to the earth ground. A continuous attenuator circuit is used to attenuate high frequency transients in the frequency range of 50 KHz to 200 MHz electrically coupled between the earth ground and the electrical load ground.